Powdered fire extinguishing composition



United States Patent 3,179,588 POWDERED FIRE EXTINGUISHING COMPOSITIONTimo Siimes, Riverside, Ontario, Canada, assignor, by

mesne assignments, to General Fire Extinguisher Corporation, Detroit,Mich., a corporation of Delaware No Drawing. Filed Dec. 19, 1960, Ser.No. 76,522 Claims. (Cl. 252-2) The present invention relates to a drypowder fire extinguishing material and, more particularly, relates to anon-caking, free flowing, finely powdered fire extinguishing compositionhaving improved water repellency characteristics, good flowcharacteristics and reduced hygroscopicity characteristics, and which issuitable for use in extinguishing all kinds of fires including burningliquids,

live electrical fires, fires of solid substances such as Wood, rubber,etc., as well as combustible metal fires, such as magnesium.

. Heretofore, dry fire extinguishing chemicals have been formulated forextinguishing various types of fires and a few of such compositions havefound commercial acceptance. In all known cases, however, priorcompositions have had one or more deficiencies such as an undesirabletendency to cake on storage, poor flow characteristics, poor resistanceto caking under elevated temperature conditions, undesirablehygroscopicity characteristics, poor waterv repellency or excessivecost. It will be appreciated that since materials employed to extinguishfires are discarded after one use that it is imperative for them to berelatively inexpensive. Suitably inexpensive materials which haveemployed in the past include the alkali metal salts of phosphoric, boricand sulfuric acids, the alkali metal carbonates and bicarbonates andsuch heretofore known compositions have relied at least partially on theliberation of carbon dioxide gas to assist in extinguishing the fires.Many of the combination materials of this type have been characterizedby poor flow characteristics.

In accordance with this invention,, it has now been found that theadvantageous fire extinguishing characteristics of the salts ofphosphoric and sulfuric acids can be utilized effectively in a drypowder fire extinguishing composition when such powders are modified toimprove their flow, hygroscopicity, and caking characteristics.

The basic components of the compositions of this invention are an alkalimetal sulfate and an ammonium phosphate which may be either thediammonium or monoarrimonium phosphate. The modifying ingredientsinclude .a silicone resin, a phenolic resin, a metal stearate and mica,The compositions may optionally include one or more of the alkalineearth metal salts of phosphoric and sulfuric acid such as barium sulfateand tri-calcium phosphate. Broadly, the compositions of this inventioninclude the above stated ingredients, in the relative proportionsspecified.

FORMULATION I Component: Parts by weight Diammonium or mono-ammoniumphosphate 35-90 All of the above ingredients should be in finely divided,or powder form and at least about 75% of the particles should passthrough a 325 mesh Tyler. screen, and the balance are preferably smallerthan 100 mesh Tyler screen, although small quantities of particleslarger than 100 mesh can be tolerated.

3,l?9,583 Patented Apr. 20, 1965 the resulting composition a moreefiicient extinguishing medium for any and all types of fires which maybe encountered.

A- preferred formulation having somewhat better overall characteristicsis set forth as Formulation II.

FORMULATION II Component: Parts by weight Diammonium phosphate 65-82Ammonium sulfate 8-14 Barium sulfate 10-16 Phenolic resin (B-stage) 2-5Mica 1 /2-2 /2 Tri-calcium phosphate 1 /2-2 /2 Silicone resin 1-3Magnesium stearate 1-2 substituted for by one or more of the namedmaterials.

In either event, the total quantity of the mixture or separatesubstitute ingredients should be Within'therange specified inFormulation I for mica.

When the proportion of mica, or a substitute is below about /2 part byWeight, no substantial improvement in flow characteristics is detectableand when more than about 5 parts by weight of mica, or its substitute ispresent, the density of the extinguishing composition becomes too low tobe practical. When, however, one of the heavier materials is substitutedfor mica, the upper limit of 5 parts by weight may be used or evenexceeded without adetriment to the flow characteristics. For example,when molybdenum disulfide or tungsten disuliide is employed as asubstitute, the upper limit may satisfaotorily range as high as 10-15parts by weight without rendering the material too light or fluffy forgood flow characteristics.

The phenolic resin component serves to modify the particle form of thepowdered phosphate and sulfate metal salts :by both agglomeration of theextremely fine :particles and elimination of needle shaped particles.The

.furaldehyde or acrolein but is preferably formaldehyde, which may besupplied as paraformaldehyde or hexamethyltetramine for condensationwith phenol in conven- 3 tional relative proportions and employingconventional reaction conditions to form B-stage reaction products.

The zinc or magnesium stearate component functions to form a moistureprotective coating which keeps the particles dry and reduceshygroscopicity, particularly during the later stages of the compoundingprocedures and prior to the actual charging of the dry material into afire extinguishing apparatus. The zinc or magnesium stearate can bereplaced by other metallic stearates such as barium or other alkalineearth stearates, in whole or in part. The use of portions of zincstearate, or its substitute in quantities above about three parts, inFormulation I, tends to cause lumping and decreases the smooth flowcharacteristics of the powder. Below about /2 part of the stearatecomponent, the powder is undesirably hygroscopic. Magnesium stearate issuperior to zinc stearate, particularly for use on extremely hightemperature fires such as combustible metal fires and is the preferredingredient for the purposes of this invention.

The silicone resin functions to form an external shell or envelope onall of the phosphate, sulfate and agglomerated particles, and this shellis continuous and imparts substantially complete water repellency to theindividual particles. The powder therefore has extremely good resistanceto caking during storage. The silicone materials which may be employedin the compositions of the present invention include organo-siliconesand preferably are those which may be applied to the particles in aliquid form. It is possible to satisfactorily employ gaseous siliconematerials such as trimethylchlorosilane, but these materials are moretroublesome to handle and apply uniformly. The silicone is preferably atrifunctional silicone which is capable of cross-linking duringpolymerization on the surface of the particles, or agglomerants in thecomposition. The silicones which are suitable react to form across-linked polysiloxane having the general formula x y z)n wherein Ris a hydrocarbon, x, y and z are whole numbers and n is the number ofstructural units in the surface formed by the polysiloxane. In thesematerials, the ratio of x/z should be less than 2 but not less than 2/3. Specific examples of suitable polysiloxane-producing materials whichmay be employed are the alkyl trihalosilanes, includingmethyltrichlorosilane, amyltrichlorosilane, octadecyltrichlorosilane,cyclohexyltrichlorosilane, etc., alkenyl trihalosilanes, includingallyltrichlorosilane, vinyltrichlorosilane, etc., the aryltrihalosilanes, including phenyltrichlorosilane, etc., the alkylalkoxysilanes, including methyltriethoxysilane,mono-methyl-diethoxysilane, etc., and alkenyl alkoxysilanes, includingvinyltriethoxysilane, etc. These, starting materials are hydrocarbonsubstituted trifunctional silicone materials and include hydrocarbonsubstituted trihalosilane silicone materials.

Other polysiloxane-producing materials which are satisfactory arecopolymers resulting from the partial hydrolysis of any of the abovelisted materials with difunctional silanes, such asdimethyl-diethoxysilane, dimethyldichlorosilane anddiphenyldihydroxysilane. These materials are solid commercially by DowCorning as DC-1107, DC-1108, by Linde Air Products Co. as X-21, X-22 andGeneral Electric as SC-87. Particularly good results have been obtainedfrom the use of Dow Corning DC- 1107, which is understood to be similarto dimethyl silicone fluid ((CH )SiO) except that many of the methylgroups have been replaced by hydrogen ator'ns. On heat curing, thepolymers cross-link at the sites of hydrogen atoms to form a coating.DC-1107 is Water-white in color, has a specific gravity between 0.995and 1.015, a viscosity at 25 C. Of 2040 centistokes, a minimum flashpoint of 200 F. and a maximum acid number of 0.02.

The compositions of this invention are compounded by first mixing theammonium phosphate, the alkali metal sulfate, the phenolic resin, andthe barium sulfate, when present, in a suitable mixing apparatus such asa ribbon mixer for 5-40 minutes. Thereafter, this mixture is pulverizedin an impact pulverizer which fractures the phenolic resin particles andcoats the surface of the phosphate and sulfate particles with thephenolic resin. After pulverizing, the mixture is classified, orscreened, and the particles are selected which pass through a 325 meshTyler screen and particles which are retained on a 100 mesh screen arerejected. A blend is then made of these particles in which at least byweight of the total particles pass through a 325 mesh Tyler screen. Thesilicone resin is then admixed with a suitable solvent to convert itinto a low viscosity liquid, for example, the normal viscosity of waterat room temperature, and this is accomplished by admixing the siliconeresin with about 25% to about 75% by volume of trichloroethylene, carbontetrachloride, isopropyl alcohol or the like. The classified and mixedparticles are then repositioned in a ribbon mixer and, while the mixeris rotating, the silicone resin-solvent blend is added to the mixture.The addition may be accomplished by slowly pouring in the siliconeresin-solid liquid or by spraying or atomizing the siliconeresin-solvent blend into the ribbon mixer. Somewhat more uniformapplication to the particles is obtained by using the spray or atomizingtechnique and this procedure is preferred. The material is mixed in theribbon mixer with the silicone resin-solvent material for approximately10 minutes and a catalyst for the silicone resin is then applied. A-suitablecatalyst for this purpose is a blend of 30 parts by weight oftin octoate (16% active ingredients) in admixture with 70 parts byweight of trichloroethylene. Other lrnown catalysts may be employed,such as iron octoate, Zinc 2-ethylhexoate, tin oleate, zinc naphthenateor triethanolamine and in any case an amount of catalyst to provideabout 2% metal, based on the silicone solids in the diluted siliconeresin solution, should be added. The proportion of trichloroethylene orother suitable solvent which is employed is not critical, but asufiicient quantity should be employed to give a fairly thin liquidwhich will uniformly coat the previously coated particles. The catalystmay be applied in the same manner in which the silicone resin solventmaterial is applied and, for this purpose, application in the atomizedspray form is also preferred. The material is tumbled in the mixer for10-15 minutes and is then dried. During drying, the material ispreferably slowly rotated and the temperature in the dryer is raisedslowly to first remove the excess solvent and thereafter to effectcuring of the silicone and the phenol formaldehyde resin coating on thesurface of the particles. The mixture should be raised to a temperatureof about 285 to about 310 F. and adequate curing is obtained in about 15minutes to an hour with excellent results being obtained from curing forabout 30 minutes. After curing, the material is taken out, againpositioned in a ribbon mixer and the additional components, mica, zincstearate, and tri-calcium phosphate are added to the mixer while thepowder is still hot, preferably in the range of about 260 F.-275 F.

The addition of the zinc stearate to the hot powder assures uniformdistribution of the zinc stearate throughout the mass and this mixingstep is satisfactorily accomplished in about 20-30 minutes. After thisfinal mixing, the blended materials are removed from the ribbon mixer,allowed to cool, and if desired, are screened to remove large particles,for example, particles larger than will pass through a 60 mesh Tylerscreen. The following examples illustrate the method of compounding andthe use of the compositions of this invention in greater detail.

Example I 87 parts of diammoniurn phosphate, 7 parts of ammonium sulfateand 8 parts of barium sulfate, 0.75 part of a phenol formaldehyde,B-stage resin, Durez resin No. 15,546, by weight, were added to a ribbonmixer and mixed for 10 minutes. Thereafter, the mixture was positionedin an impact pulverizer and screened through a 325 mesh screen.

A silicone resin-solvent mixture was prepared by admixing Dow CorningDC-1107, silicone fluid with trichloroethylene in a 50-50 mixture. Withthe mixed diammonium phosphate and ammonium sulfate particles rotatingin the ribbon mixer, sufiicient of the silicone resin-solvent blend wasatomized on the particles to equal 2 parts, by weight. The mixing wascontinued for about minutes and thereafter a catalyst for the siliconeresin was added in the same manner. The catalyst blend contained 30parts, by weight, of tin octoate (16% active ingredients) in admixturewith 70 parts, by weight, of trichloroethylene and suflicient of thiscatalyst blend was added to represent A part, by weight, of the entirecomposition. The material was tumbled in the mixer for minutes and thenslowly dried, and thereafter cured at 300. F. for minutes. While thematerial was still hot, and at a temperature in the range of 260 F.-275F. and while rotating in the ribbon mixer, 2 parts of finely powderedmica, 2 parts of magnesium stearate and 2 parts of tri-calcium phosphatewere added thereto and blended for 25 minutes. After cooling, theproduct was passed through a 60 mesh Tyler screen.

15 lbs. of this powdery composition were placed in a standard drychemical fire extinguisher, pressurized with air at 170 psi anddischarged on a wood crib Class A fire, in accordance with UnderwritersLaboratories specifications. The powder was uniformly discharged and thefire was completely extinguished in 9 seconds.

Another standard dry chemical fire extinguisher was filled with 15 lbs.of the above powdery composition and pressurized in the same manner setforth above, and discharged on a Class B fire of white naphtha gasoline,in accordance with Underwriters Laboratories specifications. The firewas completely extinguished in an average time of 12 seconds in a seriesof such applications.

The powdery composition was tested in the extinguishing of a Class Cfire for electrical conductivity in accordance with UnderwritersLaboratories specifications and found to be non-conductive.

In another test, 20 lbs. of the above powdery material was placed in astandard dry chemical fire extinguisher and discharged on a fire of 15lbs. of magnesium chips. The fire was extinguished by the use of 17 lbs.of the above powdery composition.

Example II A dry powder composition was prepared, using the sameprocedure as that described in detail in Example I, to contain 85 partsdiammonium phosphate, 12 parts ammonium sulfate, 2 parts mica, 1 partmagnesium stearate and 2 parts Dow Corning DC-1l07 silicone resin and0.75 part phenol formaldehyde resin.

A standard dry chemical fire extinguisher was loaded with 15 lbs. ofthis powdery composition, placed under 170 p.s.i. air pressure anddischarged on a wood crib Class A fire in accordance with UnderwritersLaboratories specifications. The fire was completely extinguished in 16seconds.

Example III A dry powder composition was prepared, having an identicalcomposition to that set forth in Example I and different in the respectonly that the silicone resin was applied to the mixed diammoniumphosphate and ammonium sulfate particles coated with the phenolformaldehyde resin by introducing trimethylchlorosilane in heated vaporform to the interior of the rotating ribbon mixer.

An inspection of the resulting product and testing of it in a manneridentical to that set forth in Example I showed that the material hadcomparable flow properties, water repellency properties and resistanceto moisture pick-up in the atmosphere to that of the product of ExampleI. When the material was used to extinguish Class A, B and C fires, asset forth in Example I, substantially similar results were obtained ineach case.

What is claimed is: 1

l. A dry powdery fire extinguishing composition which consistsessentially of, by weight, -90 parts an alkali metal phosphate, 5-40parts an alkali metal sulfate, /2-5 parts mica, /2-3 parts of a stearateselected from the group consisting of zinc, magnesium and alkaline earthmetal stearates, /2-6 parts a silicone resin and /z-7 parts of a B-stagephenol aldehyde condensation product, said composition being in the formof discrete particles at least 75% of which are smaller than 325 Tylerscreen mesh, said condensation product being present as a surfacecoating on said particles and said silicone resin overlying saidcondensation product surface coating.

2. A dry powdery fire extinguishing composition which consistsessentially of, by weight, 65-82 parts an alkali metal phosphate, 8-14parts an alkali metal sulfate, /2-2 /z parts mica, 1-2 parts of astearate selected from the group consisting of Zinc, magnesium andalkaline earth metal stearates, 1-3 parts a silicone resin and 2-5 partsof a B-stage phenol aldehyde condensation product, said compositionbeing in the form of discrete particles at least 75% of which aresmaller than 325 Tyler screen mesh, said condensation product beingpresent as a surface coating on said particles and said silicone resinoverlying said condensation product surface coating.

3. A dry powdery fire extinguishing composition which consistsessentially of, by weight, 35-90 parts an alkali metal phosphate, 5-40parts an alkali metal sulfate, /2-5 parts mica, up to 30 parts bariumsulfate, up to 5 parts tri-calcium phosphate and /2-3 parts of astearate selected from the group consisting of zinc, magnesium andalkaline earth metal stearates, /z-6 parts a silicone resin and /2-7parts of a B.-stage phenol aldehyde condensation product, saidcomposition being in the form of discrete particles at least 75% ofwhich are smaller than 325 Tyler screen mesh, said condensation productbeing present as a surface coating on said particles and said siliconeresin overlying said condensation product surface coating. V

4. A-dry powdery fire extinguishing composition which consistsessentially of, by weight, 65-82 parts an alkali metal phosphate, 8-14parts an alkali metal sulfate, /2-2 /z parts mica, 10-16 parts bariumsulfate, 1 /2-2 /z parts tri-calciurn phosphate, 1-2 parts of a stearateselected from the group consisting of zinc, magnesium and alkaline earthmetal stearates, 1-3 parts a silicone resin and 2-5 parts of a B-stagephenol aldehyde condensation product, said composition being in the formof discrete particles at least 75 of which are smaller than 325 Tylerscreen mesh, said condensation product being present as a surfacecoating on said particles and said silicone resin overlying saidcondensation product surface coating.

5. A method of combatting fires of burning combustible materials whichcomprises applying to said burning combustible materials, a solid, drychemical fire extinguishing composition consists essentially of, byweight, 35-90 parts an alkali metal phosphate, 5-40 parts an alkalimetal sulfate, /2-5 parts mica, /2-3 parts of a stearate selected fromthe group consisting of zinc, magnesium and alkaline earth metalstearates, /26 parts a silicone resin and /2-7 parts of a B-stage phenolaldehyde condensation product, said composition being in the form ofdiscrete particles at least 75 of which are smaller than 325 Tylerscreen mesh, said condensation product being present as a surfacecoating on said particles and said silicone resin overlying saidcondensation product surface coating.

6. A method of combatting fires of burning combustible materials whichcomprises applying to said burning combustible materials, a solid, drychemical fire extinguishing composition consists essentially of, byweight, 65-82 parts an alkali metal phosphate, 8-14 parts an alkalimetal sulfate, /2-2' /2 parts mica, 1-2 parts of a stearate selectedfrom the group consisting of zinc, magnesium and alkaline earth metalstearates,- 1-3 parts a silicone resin and 2-5 parts of a B-stage phenolaldehyde condensation product, said composition being in the form ofdiscrete particles at least 75% of which are smaller than 325 Tylerscreen mesh, said condensation product being present as a surfacecoating on said particles and said silicone resin overlying saidcondensation product surface coating.

7. A method of combatting fires of burning combustible materials whichcomprises applying to said burning combustible materials, a solid, drychemical fire extinguishing composition consists essentially of, byweight, 35-90 parts an alkali metal phosphate, 5-40 parts an alkalimetal sulfate, /2-5 parts mica, up to 30 parts barium.

sulfate, up to 5 parts tri-calcium phosphate and /23 parts of a stearateselected from the group consisting of zinc, magnesium and alkaline earthmetal stearates, /2-6 parts a silicone resin arid /2-7 parts of aB-stage phenol aldehyde condensation product, said composition being inthe form of discrete particles at least 75 of which are smaller than 325Tyler screen mesh, said condensation product being present as a surfacecoating on said particles and said silicone resin overlying saidcondensation product surface coating.

8. A method of combatting fires of burning combustible materials whichcomprises applying to said burning combustible materials, a solid, drychemical fire extinguishing composition consists essentially of, byweight, 65-82 parts an alkali metal phosphate, 8-14 parts an alkalimetal sulfate, /2-2 /2 parts mica, 10-16 parts barium sulfate, 1 /2-2 /2parts tri-calcium phosphate, 1-2 parts of a stearate selected from thegroup consisting of Zinc,'magnesium and alkaline earth'metal stearates,1-3 parts a silicone resin and 2-5 parts of a B-stage phenol aldehydecondensation product, said composition being in the form of discreteparticles at least 75 of which are smaller than 325 Tyler screen mesh,said condensation product being present as a surface coating on saidparticles and said silicone resin overlying said condensation productsurface coating.

9. A.niethod of making adry powdery: fire extinguishing compositionwhich comprises the steps of (1), mixing, in parts by Weight, 35-90parts of an alkali metal phosphate, 5-40 parts an alkali metal sulfateand /2 -7 parts a phenol formaldehyde resin, (2), screening theresulting mixture and discarding the particles which are retained on amesh screen, (3), adding to the retained particles from step (2) about/2-6 parts of a silicone resin in a solvent while said particles are inmotion, (4), adding a catalyst in an organic solvent to provide a metalconcentration of about 2%, by Weight of the silicone resin solids, saidmetal being selected from the group consisting of tin, iron andzinc andbeing added in the form of a salt thereof and (5) slowly raising thetemperature within the range of about 285 F. to about 310 F. to removethe excess solvent and to effect a cure of the silicone and phenolformaldehyde resin in said mixture.

10. A method in accordance with claim 9 wherein the product of step (5)is admixed, while at a temperature in the range of about 260 F.-275 F.with about /2-5 parts of mica, /2-3 parts of a stearate selected fromthe group consisting of zinc, magnesium and alkaline earth metalstearates, and about 1 /2-2 /2 parts tri-calcium phosphate.

References Cited by the Examiner UNITED STATES PATENTS 2,588,366 3/52Dennett 260-291 2,647,892 8/53 La Brie et al. 252-384 X 2,734,002 2/56Schoeld et al. 260-57 X 2,736,718 2/56 Webber 260-57 X 2,757,152 7/56Solomon 260-465 X 2,866,760 12/58 Haessler et al. 252-383 2,881,138 4/59Reiss 252-7 2,901,428 8/59 Schulenburg 252-7 3,017,348 1/62 Steppe etal. 252-7 X FOREIGN PATENTS 156,735 5/54 Australia. 815,712 7/59 GreatBritain.

JULIUS GREENWALD, Primary Examiner.

1.A DRY POWDERY FIRE EXTINGUISHING COMPOSITION WHICH CONSISTSESSENTIALLY OF, BY WEIGHT, 35-90 PARTS AN ALKALI METAL PHOSPHATE, 5-40PARTS AN ALKALI METAL SULFATE, 1/2-5 PARTS MICA, 1/2-3 PARTS OF ASTEARTE SELECTED FROM THE GROUP CONSISTING OF ZINC, MAGNESIUM ANDALKALINE EARTH METAL STEARATES, 1/2-6 PARTS A SILICONE RESIN AND 1/2-7PARTS OF A B-STAGE PHENOL ALDEHYDE CONDENSATION PRODUCT, SAIDCOMPOSITION BEING IN THE FORM OF DISCRETE PARTICLES AT LEAST 75% OFWHICH ARE SMALLER THAN 325 TYLER SCREEN MESH, SAID CONDENSATION PRODUCTBEING PRESENT AS A SURFACE COATING ON SAID PARTICLES AND SAID SILICONERESIN OVERLYING SAID CONDENSATION PRODUCT SURFACE COATING.
 9. A METHODFO MAKING A DRY POWDERY FIRE EXTINGUISHING COMPOSITION WHICH COMPRISESTHE STEPS OF (1), MIXING, IN PARTS BY WEIGHT, 35-90 PATS OF AN ALKALIMETAL PHOSPHATE, 5-40 PARTS AN ALKALI METAL SULFATE AND 1/2-7 PARTS APHENOL CORMALDEHYDE RESIN, (2) SCREENING THE RESULTING MIXTURE ANDDISCARDING THE PARTICLES WHICH ARE RETAINED ON A 100 MESH SCREEN, (3),ADDING TO THE RETAINED PARTICLES FROM STEP (2) ABOUT 1/2-6 PARTS OF ASILICONE RESIN INA SOLVENT WHILE SAID PARTICLES ARE IN MOTION, (4),ADDING A CATALYST IN AN ORGANIC SOLVENT TO PROVIDE A METAL CONCENTRATIONOF ABOUT 2%, BY WEIGHT OF THE SILICONE RESIN SOLIDS, SAID METAL BEINGSELECTED FROM THE GROUP CONSISTING OF TIN, IRON AND ZONC AND BEING ADDEDIN THE FORM OF A SALT THEREOF AND (5) SLOWING RAISING THE TEMPERATUREWITHIN THE RANGE OF ABOAUT 285*F. TO ABOUT 310*F. TO REMOVE THE EXCESSSOLVENT AND TO EFFECT A CURE OF THE SILICONE AND PHENOL FORMALDEHYDERESIN IN SAID MIXTURE.